1. Field of the Invention
This invention relates to special service signaling applications within a telephone network such as Foreign Exchange Subscriber (FXS), Foreign Exchange Office (FXO), Private Line Automatic Ringdown (PLAR), Foreign Exchange Ringdown (FXRD), E & M Modes 1-5, Dial Pulse Originating and Terminating (DPO, DPT), Duplex Signaling (DX), Pulse Link Repeater (PLR), Tandem Signaling (TDM) and Reverse Battery Signaling and, in particular, this invention relates to a programmable universal telephony signaling circuit that is capable of providing all special service signaling.
2. Discussion of the Prior Art
Historically, special service signaling circuits have been designed and utilized in telephony networks to provide unique signaling requirements. Each circuit was separately designed and functioned uniquely within the telephone network. The use of separate circuits, however, has created quite a burden on telephone companies who have had to stock an assortment of transmission and signaling printed circuit (PC) boards with each PC board carrying a different circuit. This is costly to operating companies in maintaining such an extensive inventory and in providing the necessary personnel to maintain the circuits and to install them in the telephone network.
One prior art approach to reduce this extensive inventory of special service circuits was to combine several related signaling applications into one board and to use switches actually located on the PC board which could be selectively activated by maintenance personnel and installers to reconfigure the PC board into one of several formats. While this somewhat aided in the inventory problem, it introduced a new concern. The manual setting of such switches introduced the problem of wrong settings which created additional overhead and maintenance costs to the telephone company.
A need exists, therefore, for a universal signaling circuit which permits a single unit to operate in one of a number of conventional signaling types and modes for fulfilling the special service signaling applications within the telephone network. Such a universal signaling circuit would eliminate the maintenance of a costly inventory since only one circuit is stocked and maintained. Such a universal signaling circuit should also be designed to eliminate the manual setting of switches and should have the ability to be configured either at the point of installation or remotely. Finally, a need exists for a universal signaling circuit which can be remotely reconfigured to function as a different special signaling circuit should the need arise.
3. Solution to the Problem
The present invention sets forth a programmable universal signaling circuit for handling special service signaling applications within a telephone network. The circuit is capable of providing at least thirty-two types of conventional telephone network special service signaling and, under the teachings of the present invention, can be adapted to provide new and other signaling features more or less than thirty-two. The universal signaling circuit of the present invention is designed to be under microprocessor control which can be programmed at the point of installation after installation, or reconfigured at a remote location at a later date. While the cost per PC board of the present invention is greater than the cost for individual prior art special service signaling PC boards, substantial savings are obtained. Because only one circuit design is utilized, only that circuit design needs to be stockpiled in inventory and maintained. This substantially reduces inventory, maintenance, and training costs. The use of a programmable universal signaling circuit also eliminates manual setting of switches, manual reading of the different types of circuit boards (since only one is used), and more trouble-free installation. Finally, because of the programmable characteristics of the universal signaling circuit of the present invention, once installed, the circuit can be reconfigured to provide a different special service signaling application from a remote location such as found in a central office.